Sheet feeder, image scanner provided with the sheet feeder, and printer provided with the image scanner

ABSTRACT

A sheet feeder includes a separation roller having a circumferential surface that contacts a first sheet to be fed first among stacked sheets and picks up the first sheet and one or more second sheets adjacent to the first sheet, a separation arm that is closer to the circumferential surface of the separation roller downstream in a feeding direction and configured to apply higher frictional resistance to the second sheets than the first sheet to feed the first sheet ahead of the second sheets, and a guide member including a guide portion that has a lower-friction surface than the separation arm and extends from the separation arm with a distal end thereof in contact with or close to the circumferential surface of the separation roller. The guide portion guides the first and second sheets along the circumferential surface of the separation roller.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. patentapplication Ser. No. 12/486,408, which was filed on Jun. 17, 2009, whichclaims priority under 35 U.S.C. §119 from Japanese Patent ApplicationNo. 2008-162298 filed on Jun. 20, 2008. The entire subject matter of theapplications are incorporated herein by reference.

BACKGROUND

1. Technical Field

The following description relates to one or more sheet feedersconfigured to feed sheets separately on a sheet-by-sheet basis andsmoothly to a scanner unit or a printer unit.

2. Related Art

As a sheet feeder, employed for an image scanner or a printer, which isconfigured to feed sheets stacked on a feed tray to a scanner unit or aprinter unit separately on a sheet-by-sheet basis, Japanese UtilityModel Provisional Publication No. SHO59-159651 discloses an AutomaticDocument Feeder (ADF) that includes a feed tray configured to be loadedwith plural document sheets thereon, a feed roller (a separation roller)that is provided at a downstream side in a sheet feeding directionrelative to the feed tray and configured to rotate in the sheet feedingdirection, a high-friction discrimination arm configured to contact thefeed roller, a low-friction film that is provided on a side of a contactsurface between the discrimination arm and the feed roller and formed tobecome narrower in the sheet feeding direction, and an urging memberconfigured to urge the discrimination arm toward the feed roller.

In the above configuration, now the following situation is assumed:easily-bendable document sheets are stacked high on the feed tray and aleading end of a sheet among the stack of document sheets that is at theclosest level to a circumferential surface of the feed roller is fed ina tangential direction of the circumferential surface of the feed rollerand then conveyed toward a surface of the discrimination arm. In thissituation, when the film is short and a leading end thereof is far at anupstream side in the sheet feeding direction away from a nipping pointbetween the feed roller and the discrimination arm, the leading end ofthe document sheet cannot establish sliding contact with a surface ofthe film at a small angle. Consequently, the leading end of the documentsheet collides directly against the high-friction surface of thediscrimination arm at an angle as large as 60 degrees. It results ingreat resistance to feeding the leading end of the document sheet in thesheet feeding direction. Nevertheless, a portion of the document sheeton an upstream side in the sheet feeding direction relative to theleading end thereof is forced to be fed to the downstream side by thecircumferential surface of the feed roller. Therefore, the upstream-sideportion of the sheet is reformed in a curled shape. A range in which thereformation of the sheet into a curled shape is caused correspondssubstantially to a width of the discrimination arm (i.e., a length ofthe discrimination arm in a direction parallel to a surface of the sheetand perpendicular to the sheet feeding direction). Thus, the reformationof the sheet is regarded as a kind of buckling.

On the contrary, when the leading end of the film is extended close tothe nipping point between the feed roller and the discrimination arm, aneffective high-friction area on the surface of the discrimination arm isreduced. Consequently, the reformation of the sheet into a curled shapeis hardly caused. However, when the leading end of the film reaches thenipping point, an operation of separating sheets cannot be achievedbetween the feed roller and the discrimination arm, and it results inmultiple-sheet feeding. Nonetheless, a positional relationship betweenthe feed roller and the discrimination arm that may vary within aproduction tolerance unfortunately makes it difficult to locate theleading end of the film in an appropriate position.

Japanese Patent Provisional Publication No. HEI6-227693 (see FIGS. 1 to6 in the Publication) discloses a sheet feeder that includes, at an endon a sheet feeding side, a rubber feed roller driven to rotate and ahigh-friction separation arm configured to contact an uppercircumferential surface of the feed roller. The sheet feeder furtherincludes a metal plate regulator disposed such that a distal end thereofpresses a portion, of a back surface of the separation arm, near anipping point between the separation arm and an upper circumferentialsurface of the feed roller. Thus, a gap between the feed roller and theseparation arm is regulated to a distance such that a single sheetpasses therethrough.

Further, the sheet feeder includes lower spring members disposed at bothsides in a width direction of the separation arm. Bases of the lowerspring members formed from metal plates are fixed to a bracket togetherwith the separation arm. The bases of the lower spring members are fixedto a surface of the separation arm that faces the circumferentialsurface of the feed roller. Furthermore, free ends of the lower springmembers are extended up to such a position, at an upstream side in thesheet feeding direction relative to the nipping point, as to nearlycontact the upper circumferential surface of the feed roller. In thisconfiguration, sheets of a stack of sheets on a feed tray are insertedinto between the upper circumferential surface of the feed roller andthe lower spring members in an overlapping state. At this time, themultiple-sheet feeding can allegedly be prevented by such an operationthat a sheet, which is in contact with the upper circumferential surfaceof the feed roller, proceeds ahead of a sheet which is receiving highfrictional resistance while contacting the separation arm. Theconfiguration has a problem that the number of sheets settable on thefeed tray is limited to as many as ten.

On the other hand, Japanese Patent Publication No. 3567609 (hereinafter,simply referred to as '609 Publication) (see FIGS. 1 and 2 in '609Publication) and FIGS. 14A and 14B disclose a document feeder thatincludes a separation arm 101, a first plate spring 103, and a secondplate spring 102. A back surface side of the separation arm 101 issupported by the first plate spring 103 which is configured to beelastic. An engagement portion 104 bent to get up from a base of thefirst plate spring 103 is engaged with an engagement hole 105 providedat a base of the separation arm 101. Thereby, a surface of a distal endside of the separation arm 101 is pressed by a circumferential surfaceof a feed roller 100.

A base of the second plate spring made of metal is fixed to a housingsuch as a cover member, together with a base of the first plate spring.The second plate spring 102 has two-forked distal end portions thatextend from the base of the second plate spring 102 along both sides ina width direction of the separation arm 101. Each of the two-forkeddistal end portions of the second plate spring 102 has a distal endbending portion 102 a formed to bend in a V-shape when laterally viewed.The length of the feed roller 100 in the axial direction thereof islarger than the distance between the two distal end bending portions 102a. When laterally viewed, the two distal end bending portions 102 a arelocated between a position 108 where a leading end of a top sheet ofsheets 106 stacked at an upstream side in the sheet feeding directioncontacts the circumferential surface of the feed roller 100 and aposition 107 where the separation arm 101 contacts the circumferentialsurface of the feed roller 100 (i.e., a nipping point where a sheet isnipped between the separation arm 101 and the circumferential surface ofthe feed roller 100. Further, the distal end bending portions 102 a aredisposed to be in contact with the circumferential surface of the feedroller 100 or as close thereto as possible. According to the aboveconfiguration, since an angle θ between the separation arm 101 and thesheets 106 can be set larger, the distal end bending portions 102 a canbe shifted to a downstream side in the sheet feeding directionrelatively in comparison with a conventional configuration. Further, asan angle φ between the distal end bending portions 102 a and the sheets106 is set large, the sheets 106 are allegedly separated more certainlyso as to avoid a problem such as the multiple-sheet feeding and no-sheetfeeding.

SUMMARY

In the meantime, in '609 Publication, when a stack volume [height (H1)]of the sheets 106 placed at an upstream side in the sheet feedingdirection is large, and each of the sheets 106 is thin andeasily-bendable, the following failure may be caused. In the position108 where the leading end of the top sheet of the sheets 106 contactsthe circumferential surface of the feed roller 100, the leading end ofthe top sheet is separated and guided in a tangential direction of thecircumferential surface of the feed roller 100. In the positions wherethe two distal end bending portions 102 a exist, the leading end of thesheet 106 separated is introduced into between the distal end bendingportions 102 a and the circumferential surface of the feed roller 100while being pushed down by an elastic force of the distal end bendingportions 102 a. Thereby, the leading end of the sheet 106 is not bent toexcess.

However, in the position within the width of the separation arm 101where the two distal end bending portion 102 do not exist, the leadingend of the sheet 106 collides against the high-friction surface of theseparation arm 101, and the leading end of the sheet 106 is conveyed inthe sheet feeding direction while receiving high frictional resistance.Further, the sheet 106 is pushed to a downstream side in the sheetfeeding direction by a feeding force given by the circumferentialsurface of the feed roller 100. Thus the sheet 106 is fed to thedownstream side in the sheet feeding direction in a state where theportion of the sheet 106 pushed by the feed roller 100 is reformed in acurled shape.

After that, the leading end of the sheet 106 is conveyed to the nippingpoint 107 along the surface of the separation arm 101. Accordingly, theleading end of the easily-bendable sheet 106 is conveyed to thedownstream side in the sheet feeding direction with the curled shapeleft partially at a portion thereof within the width of the separationarm 101. Consequently, after document scanning or image printing, thesheet 106 is ejected with the curled shape left at the leading endthereof.

Aspects of the present invention are advantageous to provide one or moreimproved sheet feeders that make it possible to prevent multiple-sheetfeeding and reformation of a leading end of a sheet into a curled shapethat might be caused when the leading end of the sheet directly collidesagainst a high-friction surface of a separation arm in an attempt tofeed highly stacked easily-bendable sheets separately on asheet-by-sheet basis through a cooperative operation between aseparation roller (a feed roller) and the separation arm.

According to aspects of the present invention, a sheet feeder isprovided, which is configured to feed sheets in a predetermineddirection sequentially on a sheet-by-sheet basis. The sheet feederincludes a loading portion configured to be loaded with a stack ofsheets to be fed, a separation roller configured such that acircumferential surface thereof contacts a leading end of a first sheetto be fed first among the stack of sheets on the loading portion in acontact point and picks up the first sheet and one or more second sheetsadjacent to the first sheet from the stack of sheets, a separation armconfigured to become closer to the circumferential surface of theseparation roller downstream in the predetermined direction so as to nipthe first sheet and the second sheets picked up by the separation rollerin a nipping point between the separation arm and the circumferentialsurface of the separation roller, the separation arm adapted to applyhigher frictional resistance to the second sheets than that to the firstsheet near the nipping point so as to feed the first sheet separatelyahead of the second sheets in cooperation with the separation roller, anurging member configured to urge the separation arm toward theseparation roller, and a guide member having a guide portion with alower-friction surface than the separation arm, the guide portionconfigured to extend from the separation arm with a distal end thereofbeing in contact with or close to the circumferential surface of theseparation roller, the guide portion adapted to contact the first sheetand the second sheets picked up by the separation roller and guide thefirst sheet and the second sheets to proceed along the circumferentialsurface of the separation roller between the contact point and thenipping point.

In some aspects of the present invention, when easily-bendable documentsheets are stacked high on the loading portion, the leading end of thefirst sheet of the document sheets establishes contact with thecircumferential surface of the separation roller in the contact point,and thereafter the first sheet and one or more second sheets adjacent tothe first sheet are fed toward the separation arm in a tangentialdirection in the contact point on the circumferential direction of theseparation roller. Since the guide portion of the guide member extendsfrom the separation arm with the distal end thereof being in contactwith or close to the circumferential surface of the separation roller,the leading ends of the first sheet and the second sheets certainlycollide against the guide portion when proceeding to the separation arm.At this time, the guide portion, which has a low-friction surface, iselastically bent and forms a gap through which the first sheet and thesecond sheets can pass.

Further, in some aspects of the present invention, the guide portion isconfigured to guide the first sheet and the second sheets to proceedalong the circumferential surface of the separation roller between thecontact point and the nipping point at a downstream side in a sheetfeeding direction (the predetermined direction) relative to the contactpoint.

Accordingly, when the first sheet and the second sheets are guided alongthe circumferential surface of the separation roller, the leading end ofa sheet closer to the circumferential surface of the separation rolleris fed ahead of the leading end of the adjacent sheet. Consequently, theleading ends of the first sheet and the second sheets are smoothly fedto the nipping point between the separation roller and the separationarm, forming a wedge shape when viewed in an axial direction of theseparation roller. Additionally, near the nipping point, owing to ahigher frictional resistance from the separation arm than that from theguide portion, the second sheets other than the first sheet areprevented from proceeding. Thereby, since only the first sheet is fedseparately ahead of the second sheets, it is possible to avoidmultiple-sheet feeding. Thus, since the first sheet and the secondsheets advance substantially parallel to a surface of the separationarm, it is possible to prevent the leading ends of the sheets from beingreformed in a curled shape in a conventional fashion.

It is noted that the aforementioned first sheet denotes a sheet that isthe closest to the circumferential surface of the separation rolleramong the stack of sheets loaded on the loading portion. Therefore, whenthe separation arm is disposed below the separation roller and pluralsheets are stacked on the separation arm, the first sheet is a top sheetof the stacked sheets. On the contrary, when the separation arm isdisposed above the separation roller and plural sheets are stackedbetween the back surface of the separation arm and the circumferentialsurface of the separation roller, the first sheet is a bottom sheet ofthe stacked sheets.

Further, the guide portion may be formed by bending the guide member soas to get up at an appropriate angle from a surface of the separationarm with the distal end thereof being in contact with or close to thecircumferential surface of the separation roller. In this case, eventthough the guide portion is pushed down in sheet feeding to such anextent as to lie along the surface of the separation arm, the distal endof the guide portion never reaches the nipping point between theseparation roller and the separation arm. Thus, it is possible toprevent the multiple-sheet feeding.

According to aspects of the present invention, further provided is animage scanner, which includes a sheet feeder configured to feed documentsheets in a predetermined direction sequentially on a sheet-by-sheetbasis, and a scanner unit configured to scan images on the documentsheets fed by the sheet feeder. The sheet feeder includes a loadingportion configured to be loaded with a stack of sheets to be fed, aseparation roller configured such that a circumferential surface thereofcontacts a leading end of a first sheet to be fed first among the stackof sheets on the loading portion in a contact point and picks up thefirst sheet and one or more second sheets adjacent to the first sheetfrom the stack of sheets, a separation arm configured to become closerto the circumferential surface of the separation roller downstream inthe predetermined direction so as to nip the first sheet and the secondsheets picked up by the separation roller in a nipping point between theseparation arm and the circumferential surface of the separation roller,the separation arm adapted to apply higher frictional resistance to thesecond sheets than that to the first sheet near the nipping point so asto feed the first sheet separately ahead of the second sheets incooperation with the separation roller, an urging member configured tourge the separation arm toward the separation roller, and a guide memberhaving a guide portion with a lower-friction surface than the separationarm, the guide portion configured to extend from the separation arm witha distal end thereof being in contact with or close to thecircumferential surface of the separation roller, the guide portionadapted to contact the first sheet and the second sheets picked up bythe separation roller and guide the first sheet and the second sheets toproceed along the circumferential surface of the separation rollerbetween the contact point and the nipping point.

In some aspects of the present invention, the image scanner configuredas above can provide the same effects as the aforementioned sheetfeeder.

According to aspects of the present invention, further provided is aprinter, which includes an image scanner that includes a sheet feederconfigured to feed document sheets with images thereon in apredetermined direction sequentially on a sheet-by-sheet basis, and ascanner unit configured to scan the images on the document sheets fed bythe sheet feeder, a feed unit configured to feed print sheets, and aprinter unit configured to print the images scanned by the scanner unitonto the print sheets fed by the feed unit. The sheet feeder includes aloading portion configured to be loaded with a stack of sheets to befed, a separation roller configured such that a circumferential surfacethereof contacts a leading end of a first sheet to be fed first amongthe stack of sheets on the loading portion in a contact point and picksup the first sheet and one or more second sheets adjacent to the firstsheet from the stack of sheets, a separation arm configured to becomecloser to the circumferential surface of the separation rollerdownstream in the predetermined direction so as to nip the first sheetand the second sheets picked up by the separation roller in a nippingpoint between the separation arm and the circumferential surface of theseparation roller, the separation arm adapted to apply higher frictionalresistance to the second sheets than that to the first sheet near thenipping point so as to feed the first sheet separately ahead of thesecond sheets in cooperation with the separation roller, an urgingmember configured to urge the separation arm toward the separationroller, and a guide member having a guide portion with a lower-frictionsurface than the separation arm, the guide portion configured to extendfrom the separation arm with a distal end thereof being in contact withor close to the circumferential surface of the separation roller, theguide portion adapted to contact the first sheet and the second sheetspicked up by the separation roller and guide the first sheet and thesecond sheets to proceed along the circumferential surface of theseparation roller between the contact point and the nipping point.

In some aspects of the present invention, the printer configured asabove can provide the same effects as the aforementioned sheet feederand image scanner.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

FIG. 1 is a perspective view of a Multi-Function Peripheral (MFP) thatincorporates therein an image scanner provided with a sheet feeder in afirst embodiment according to one or more aspects of the presentinvention.

FIG. 2 is a perspective view of the image scanner provided with thesheet feeder in the first embodiment according to one or more aspects ofthe present invention.

FIG. 3 is a front view of the image scanner in the first embodimentaccording to one or more aspects of the present invention.

FIG. 4 is a perspective view of the image scanner in a state where acover is opened in the first embodiment according to one or more aspectsof the present invention.

FIG. 5 is a perspective view of the image scanner in a state where thecover is removed therefrom in the first embodiment according to one ormore aspects of the present invention.

FIG. 6 is a perspective view of the image scanner in a state where thecover, a separation roller, and a case are removed therefrom in thefirst embodiment according to one or more aspects of the presentinvention.

FIG. 7 is a cross-sectional enlarged front view showing a main part of aseparation feed mechanism in the first embodiment according to one ormore aspects of the present invention.

FIG. 8A is a perspective view showing an assembly of a separation arm, aguide member, and a spring plate included in the separation feedmechanism in the first embodiment according to one or more aspects ofthe present invention.

FIG. 8B is a perspective view showing an exploded state of theseparation arm, the guide member, and the spring plate included in theseparation feed mechanism in the first embodiment according to one ormore aspects of the present invention.

FIG. 9 is a diagram for illustrating operations of the separation feedmechanism in the first embodiment according to one or more aspects ofthe present invention.

FIG. 10A shows an assembly and an exploded state of a separation arm, aguide member, and a spring plate included in a separation feed mechanismin a second embodiment according to one or more aspects of the presentinvention.

FIG. 10B is a cross-sectional front view of the assembly of theseparation arm, the guide member, and the spring plate included in theseparation feed mechanism in the second embodiment according to one ormore aspects of the present invention.

FIG. 11A is a diagram for illustrating operations of the separation feedmechanism in the second embodiment according to one or more aspects ofthe present invention.

FIG. 11B is a cross-sectional view of the separation feed mechanismalong a line XI-XI shown in FIG. 11A in the second embodiment accordingto one or more aspects of the present invention.

FIG. 12A is a cross-sectional side view schematically showing a powertransmission mechanism for transmitting a driving force to theseparation roller in the first embodiment according to one or moreaspects of the present invention.

FIG. 12B is a cross-sectional view of the power transmission mechanismalong a line XIIB-XIIB shown in FIG. 12A in the first embodimentaccording to one or more aspects of the present invention.

FIG. 13 is a cross-sectional enlarged front view of the separation feedmechanism for illustrating a bank member and a downstream nipping pointin the first embodiment according to one or more aspects of the presentinvention.

FIG. 14A is a diagram for illustrating operations of a separation feedmechanism in a prior art.

FIG. 14B schematically shows a configuration of the separation feedmechanism in the prior art.

DETAILED DESCRIPTION

It is noted that various connections are set forth between elements inthe following description. It is noted that these connections in generaland, unless specified otherwise, may be direct or indirect and that thisspecification is not intended to be limiting in this respect.

Hereinafter, embodiments according to aspects of the present inventionwill be described with reference to the accompanying drawings. In theembodiments, aspects of the present invention are applied to a sheetfeeder 2 incorporated in an image scanner 1 of a Multi-FunctionPeripheral (MFP) 300 provided with a facsimile function, a scannerfunction, a copy function, and a printer function.

The image scanner 1 of a first embodiment includes a main body case 3placed on a housing (not shown) of the MFP 300, a cover body 4 attachedto a rear end of the main body case 3 through a hinge (not shown)rotatably in the vertical direction, and an Automatic Document Feeder(ADF) (the sheet feeder 2) provided at a side on the cover body 4. On anupper surface of the main body case 3 that is exposed when the coverbody 4 is opened, a large-sized glass plate 5 (see FIG. 5) for a staticdocument is horizontally fixed. Further, on a side of the upper surfaceof the main body case 3, an elongated glass plate 6 for a fed documentis horizontally fixed. Beneath the glass plates 5 and 6, a scanner unit8 such as a line image sensor is provided, which is configured to renderlight emitted by a light source incident onto a document through theglass plates 5 and 6, converge the light reflected by the document ontoa light receiving element through a lens, and convert the intensity ofthe light received by the light receiving element into an electricsignal. It is noted that the scanner unit 8 is configured to betranslated in a left-to-right direction (see FIG. 3) along a guide shaftby a known driving mechanism.

In the first embodiment, the scanner unit 8 is a Contact Image Sensor(CIS), but it may be a Charge Coupled Device (CCD). When document sheets9 (see FIG. 7) are scanned while being fed by the sheet feeder 2, thescanner unit 8 is rendered still under a scanning position 12 of theglass plate 5. Meanwhile, when a document sheet 9 is placed on the glassplate 6 with a surface having images and/or characters thereon up andscanned, the scanner unit 8 is translated along a lower surface of theglass plate 6 in the left-to-right direction (see FIG. 3). It is notedthat a holding member (not shown) configured with a sponge and a whiteboard is provided on a lower surface of the cover body 4.

As illustrated in FIGS. 2 and 4, a cover 7 that covers an upper side ofthe sheet feeder 2 is placed between a pair of side covers 4 a providedat a left side of the cover body 4 in FIG. 2. The cover 7 is attachedrotatably around a hinge (not shown) provided at a left end of the pairof side covers 4 a.

[Sheet Feeder]

The sheet feeder 2 includes a feed unit 10 that has a feed tray 10 a anda document loading table 14, a separation feed mechanism 11 configuredto separate the document sheets 9 stacked on the feed unit 10 and feedthe document sheets 9 sequentially on a sheet-by-sheet basis, and aconveyer unit configured to convey the document sheets 9 to theaforementioned scanning position 12 and eject the scanned sheets 9 ontoa catch tray 13. A document carrying path is formed in a U-shape suchthat the document sheets 9 are conveyed from the separation feedmechanism 11 to the catch tray 13 via the scanning position 12. Thecatch tray 13 is formed on the cover body 4. The feed unit 10 and thefeed tray 10 a are provided above the catch tray 13 and tilted down tothe separation feed mechanism 11 (see FIGS. 1 and 2). The conveyer unitincludes plural feed rollers 15 (see FIGS. 3 to 6) and a U-turn guide 16(see FIG. 4). The feed rollers 15 are configured with a large diameterto form a U-turn portion and disposed at a downstream side relative tothe scanning position 12 on the document carrying path at intervals of apredetermined distance. The U-turn guide 16 is provided on an innersurface of the cover 7 so as to cover left halves of outercircumferential surfaces of the feed rollers 15 a predetermined distanceaway from the feed rollers 15 such that a document sheet can passtherethrough. Accordingly, when the document sheets 9 are stacked on thefeed unit 10 and the feed tray 10 a with image formed surfaces thereofup, a document sheet 9 passes, with the image formed surface thereofdown, through the scanning position 12 on the U-shaped document carryingpath.

[Separation Feed Mechanism]

Subsequently, a configuration of the separation feed mechanism 11 willbe set forth in detail. As illustrated in FIGS. 3 to 6, the separationfeed mechanism 11 is disposed near a lower end of the document loadingtable 14 of the feed unit 10 on which the document sheets 9 are stacked.The separation feed mechanism 11 includes a separation roller 20disposed above the document loading table 14, a pickup roller 21, aseparation arm 23 configured to protrude upward from an attachment hole22 of the document loading table 14 and contact a lower side of acircumferential surface of the separation roller 20, a metal springplate 24 configured to press the separation arm 23 against theseparation roller 20, and a guide member 25 disposed on an upper surfaceof the spring plate 24.

The separation roller 20 and the pickup roller 21 are disposed within acase 26 configured to open down. A driving force to rotate theseparation roller 20 is transmitted to a transmission gear 28 which isattached to an end of a drive shaft 27 configured to rotate inconjunction with the separation roller 20 via a transmission mechanism(not shown) provided in one of the side covers 4 a. The separation arm23, the case 26, and the separation roller 20 are located in a center ofthe document loading table 14 in a width direction (i.e., theleft-to-right direction, which is perpendicular to a sheet feedingdirection in which the document sheets 9 are conveyed and parallel tosurfaces of the document sheets 9). A length of the separation roller 20in the width direction is set shorter than a length of the documentloading table 14 in the width direction. Thus, since the separationroller 20 is disposed in a central position of the document loadingtable 14 in the width direction, regardless of a width size of thedocument sheets 9, the separation roller 20 can always establish contactwith central portions of the document sheets 9 in the width direction.On an outer circumferential surface of a sleeve 20 a of the separationroller 20, a surface layer 29 is provided which is made of high-frictionmaterial such as rubber. Meanwhile, the separation arm 23 is made ofhigh-friction material such as rubber and cork.

As illustrated in FIG. 12B, a driving force is transmitted from a firsttransmission gear 30 a formed at a side of the separation roller 20, viaa second transmission gear 30 b rotatably borne within the case 26, to athird transmission gear 30 c formed at a side of the pickup roller 21.At this time, the separation roller 20 and the pickup roller 21 arerotated in the same direction at substantially the same circumferentialvelocity. As substitute for the above gears, a timing belt may be woundaround respective sides of the separation roller 20 and the pickuproller 21.

As illustrated in FIGS. 8A and 8B, plural engagement portions 31 a, 31b, and 31 c (in the first embodiment, three engagement portions providedin their respective directions) are formed to be cut and got up from abase of the spring plate 24. With the engagement portions 31 a, 31 b,and 31 c fitted into a rectangular attachment hole 32 formed at a baseof the separation arm 23, An attachment attitude of the separation arm23 is held relative to the spring plate 24. The spring plate 24 is bentat an intermediate portion 24 a thereof in a downward V-shape, andsupports a distal end side of a back surface of the separation arm 23with a distal end portion 24 b of the spring plate 24. As shown in FIG.7, both the bases of the spring plate 24 and the separation arm 23 areengaged in an unmovable manner with synthetic resin support frames 33 aand 33 b of the document loading table 14.

In addition, the guide member 25, which is made of low-friction materialsuch as PET (polyethylene terephthalate resin or polyethylene resin)film material, is formed as a strip that is long in the sheet feedingdirection and short in the width direction. Further, the guide member 25includes a folded portion 25 a that is provided at a base thereof andformed in a rectangle U-shape. The folded portion 25 a is partiallypinched between a right end wall of the attachment hole 32 of theseparation arm 23 and the engagement portion 31 c, and fitted into theattachment hole 32 in contact with a right end portion of the separationarm 23. Hence, the guide member 25 is fixed in a manner unmovable in afront-to-rear direction or the left-to-right direction.

As illustrated in FIGS. 8A and 8B, the guide member 25 includes anintermediate portion 25 b disposed in contact with or close to an uppersurface of the separation arm 23, and a guide portion 25 c provided at adistal end of the guide member 25. The guide portion 25 c of the guidemember 25 is tilted upward at an appropriate acute angle θ1 so as to beaway from a nipping point N on the upper surface of the separation arm23 (see FIG. 9).

In the first embodiment, the separation roller 20 has a diameter as longas 27 mm and a dimension in the width direction longer than that (30 mmto 50 mm) of the separation arm 23. Further, the guide member 25 has athickness of about 0.25 mm, and the guide portion 25 c (a portionconfigured to get up from the upper surface of the separation arm 23) aslong as 5 mm to 6 mm. Furthermore, the angle θ1 is about 20 degrees to60 degrees. A distal end of the guide portion 25 c is desired to be incontact with the circumferential surface of the separation roller 20,yet may be disposed to be as close to the circumferential surface of theseparation roller 20 as possible. As illustrated in FIG. 9, in a sideview in the front-to-rear direction, a point where the guide portion 25c begins to get up from the upper surface of the separation arm 23 islocated between a contact point S where a top sheet of the documentsheets 9 stacked on the separation arm 23 establishes contact with thecircumferential surface of the separation roller 20 and the nippingpoint N where the circumferential surface of the separation roller 20and the upper surface of the separation arm 23. Furthermore, a point M(hereinafter, referred to as a “distal end M” of the guide portion 25 c)where the distal end of the guide portion 25 c establishes contact withthe circumferential surface of the separation roller 20 is locatedbetween the contact point S and the nipping point N.

According to the aforementioned configuration, referring to FIGS. 7 and9, explanation will be given about operations of sheet separation andsheet feeding when the document sheets 9 stacked on the document loadingtable 14 are evaluated as many as 50 sheets (as high as an estimatedheight H1 of 5 mm) in volume of normal sheets. When the document sheets9 of the above predetermined volume, stacked on the document loadingtable 14, are pushed toward the pickup roller 21, the pickup roller 21turns upward around the drive shaft 27 together with the case 26, andthe document sheets 9 stacked can be pushed until the sheets 9 come intocontact with the circumferential surface of the separation roller 20. Itis noted that, according to a configuration mentioned below, the pickuproller 21 may be configured to be rotatable freely when the drive shaft27 is stopped. In addition, a driven pinch roller 34 is disposed belowthe pickup roller 21. The driven pinch roller 34 is configured to befreely rotatable and to partially protrude from the surface of thedocument loading table 14.

When the drive shaft 27 is rotated, for example, in response to aninstruction to scan the document sheets 9, and thereby the separationroller 20 and the pickup roller 21 are rotated in synchronization witheach other, a leading end of the top sheet 9 of the document sheets 9stacked on the document loading table 14 comes into contact with thecircumferential surface of the separation roller 20 at the contact pointS. After that, one or a few sheets 9, including the top sheet 9, are feddownward in a tangential direction S1 at the contact point S on thecircumferential surface of the separation roller 20. The guide portion25 c, which is elastic, is tilted upward so as to be away from the uppersurface of the separation arm 23 with the distal end M thereof being incontact with or close to the circumferential surface of the separationroller 20. Hence, when proceeding obliquely down toward the uppersurface of the separation arm 23, leading ends of the one or more sheets9 certainly collide against the guide portion 25 c. Since the guideportion 25 c is provided with a low-friction surface and configured as awhole to be elastic, the guide portion 25 c bows down around a jointbetween the guide portion 25 c and the intermediate portion 25 b alongwith the proceeding of the leading ends of the one or more sheets 9. Itleads to a gap formed between the guide portion 25 c and thecircumferential surface of the separation roller 20 so as to allow oneor more sheets 9 to pass therebetween (see a double-dashed chain line inFIG. 8).

Meanwhile, the leading ends of the one or more sheets 9 are guided in adirection M1 to be closer to the circumferential surface of theseparation roller 20. In this situation, the leading end of the topsheet 9 closest to the circumferential surface of the separation roller20 goes ahead, and the leading ends of the other underlying adjacentsheets 9 go behind, forming a wedge shape in a side view thereof.Consequently, the leading ends of the sheets 9 are smoothly fed to thenipping point N where the circumferential surface of the separationroller 20 contacts the separation arm 23 (see FIG. 9). Near the nippingpoint N, owing to frictional resistance from the separation arm 23, thesheets 9 other than the top sheet 9 are prevented from proceeding, andthe top sheet 9 is only fed separately from the other sheets 9.Accordingly, these sheets 9 proceed substantially parallel to the uppersurface of the separation arm 23, and thus it is possible to prevent theleading ends of the sheets 9 from being reformed in a curled shape in aconventional fashion.

As described above, the guide member 25 is bent at the joint between theintermediate portion 25 b and the guide portion 25 c such that the guideportion 25 c gets up from the upper surface of the separation arm 23 tobe in contact with or close to the circumferential surface of theseparation roller 20. Therefore, even though the nipping point N betweenthe circumferential surface of the separation roller 20 and theseparation arm 23 is somewhat shifted to an upstream side or adownstream side in the sheet feeding direction due to a positional errorof the guide member 25 attached relative to the separation arm 23 orpositional errors of the actually attached separation roller 20 andseparation arm 23 relative to their design values, the leading ends ofthe top sheet 9 and the other underlying adjacent sheets 9, which arefed by the rotation of the separation roller 20, can certainly come intocontact with the guide portion 25 c.

In other words, even though the easily-bendable document sheets 9 to befed are highly stacked, it is possible to easily attain an operation ofcertainly separating and feeding the document sheets 9 on asheet-by-sheet basis with the leading ends of the document sheets 9 notreformed into a curled shape without multiple-sheet feeding or no-sheetfeeding. Further, it is possible to incorporate the separation feedmechanism 11 into the sheet feeder 2 more easily.

Subsequently, a separation feed mechanism 11 in a second embodiment willbe described with reference to FIGS. 9A, 9B, 10A, and 10B. In the secondembodiment, configurations of a separation roller 20 and a pickup roller21 are the same as those in the first embodiment. In addition,configurations of a separation arm 23 and a spring plate 24 adapted topress the separation arm 23 from beneath against a circumferentialsurface of the separation roller 20 are the same as those in the firstembodiment.

A guide member 35, which is made of low-friction material such as PET(polyethylene terephthalate resin or polyethylene resin) film material,is designed to be shorter in the width direction (namely, in thefront-to-rear direction perpendicular to the sheet feeding direction)than the separation arm 23. In the second embodiment, the guide member35 includes a flat base portion 35 a and an intermediate portion 35 bthat are provided at a side of a back surface of the separation arm 23.The guide member 35 further includes a rectangular attachment hole 36formed in the base portion 35 a. With the attachment hole 36 engagedwith plural engagement portions 31 a, 31 b, and 31 c (in the secondembodiment, three engagement portions provided in their respectivedirections) formed to be cut and got up from the base of the springplate 24 in contact with outer surfaces of the engagement portions 31 a,31 b, and 31 c, the position and the posture of the guide member 35 areregulated.

The guide member 35 further includes a guide portion 35 c bent up fromthe intermediate portion 35 b of the guide member 35. The guide portion35 c is provided to extend toward the circumferential surface of theseparation roller 20 through a window hole 37 formed in a distal endside of the separation arm 23 (a side closer to the nipping point N ofthe separation arm 23 with the separation roller 20) (see FIG. 11A). Theportion 35 c may be bent up from the intermediate portion 35 b of theguide member 35 in the following two forms. One is, as illustrated inFIGS. 10A and 10B, a form of the guide portion 35 c got up at a smallangle θ2 relative to the separation arm 23 so as to contact thecircumferential surface of the separation roller 20 after once being gotup at an angle as large as 90 degrees. The other is, as illustrated inFIG. 11A, a form of the guide portion 35 c directly bent up at an acuteangle θ3 from the intermediate portion 35 b of the guide member 35.Furthermore, a distal end portion of the guide members 25 c or 35 c mayinclude a portion slightly bent down.

In any of the above forms, substantially the same separating operationas the first embodiment makes it possible to separate and feed the topsheet 9 and the plural underlying adjacent sheets 9 certainly on asheet-by-sheet basis without reformation of the leading ends of thesheets 9 into a curled shape. In other words, when the document sheets 9stacked on the document loading table 14 are evaluated as many as 50sheets (as high as an estimated height H1 of 5 mm) in volume of normalsheets, after the leading end of the top sheet 9 contacts thecircumferential surface of the separation roller 20 in theaforementioned contact point S, one or a few sheets 9 including the topsheet 9 are fed in the tangential direction S on the circumferentialsurface of the separation roller 20. The elastic guide portion 35 c isconfigured to get up from the upper surface of the separation arm 23with the distal end M thereof in contact with or close to thecircumferential surface of the separation roller 20. Therefore, when theleading ends of the plural sheets 9 proceed obliquely downward to theupper surface of the separation arm 23, each of the leading ends of theplural sheets 9 certainly collides against the guide portion 35 c. Sincea frictional coefficient between the sheets 9 and the surface of theguide portion 35 c is low and the guide portion 35 c is configured as awhole to be elastic, the guide portion 35 c is bent down as the leadingends of the plural sheets 9 proceed. Thus, a gap through which theplural sheets 9 can pass is formed between the distal end M of the guideportion 35 c and the circumferential surface of the separation roller 20(see a double-dashed chain line in FIG. 11A).

The leading ends of the plural sheets 9 are guided in the direction M1to be closer to the circumferential surface of the separation roller 20.In this situation, the leading end of the top sheet 9 closest to thecircumferential surface of the separation roller 20 goes ahead, and theleading ends of the other underlying adjacent sheets 9 go behind,forming a wedge shape in a side view thereof. Consequently, the leadingends of the sheets 9 are smoothly fed to the nipping point N where thecircumferential surface of the separation roller 20 contacts theseparation arm 23 (see FIG. 11A). Near the nipping point N, owing tofrictional resistance from the separation arm 23, the sheets 9 otherthan the top sheet 9 are prevented from proceeding, and the top sheet 9is only fed separately from the other sheets 9. Accordingly, thesesheets 9 proceed substantially parallel to the upper surface of theseparation arm 23, and thus it is possible to prevent the leading endsof the sheets 9 from being reformed in a curled shape in a conventionalfashion.

FIGS. 12A and 12B schematically show a configuration of the separationroller 20 attached to the drive shaft 27. The drive shaft 27, which is ametal round bar, includes an attachment hole 41 formed substantially ata center in an axis line direction of the drive shaft 27 with a diameterslightly larger than that of a pin 40 and a depth two thirds as long asthe diameter of the drive shaft 27. The attachment hole 41 of the driveshaft 27 is configured to stand the pin 40 in a direction perpendicularto the axis line direction of the drive shaft 27. Further, the driveshaft 27 includes a through hole 42 with a diameter smaller than that ofthe attachment hole 41. The through hole 42 is formed to follow theattachment hole 41 and penetrate a region of the drive shaft 27 wherethe attachment hole 41 is not formed. Thus, by forming the attachmenthole 41 and the through hole 42 to penetrate the drive shaft 27, whenthe drive shaft 27 is entirely plated, plating liquid passes through theattachment hole 41 and the through hole 42, and inner circumferentialsurfaces of the attachment hole 41 and the through hole 42 are plated aswell.

Meanwhile, the separation roller 20 includes a ring-shaped canopy 43integrally formed on one side of the sleeve 20 a thereof and anengagement projection 44 integrally formed on an end face of the sleeve20 a at an inner circumferential side relative to the canopy 43. The pin40 has a length set to be slightly shorter than a distance between abottom surface of the attachment hole 41 and an inner circumferentialsurface of the canopy 43 (see FIGS. 12A and 12B). In the state where thedrive shaft 27 is inserted into a central hole of the separation roller20 and an attachment hole of the case 26 and the attachment hole 41 andthe through hole 42 are located outside the canopy 43 of the separationroller 20, the pin 40 is fitted in the attachment hole 41. Subsequently,a Ω-shaped snap ring 45 is engaged with an attachment groove providedaround the drive shaft 27 at a side across the separation roller 20 fromthe pin 40 (near a right outside surface of the case 26 in FIG. 12A). Inthis situation, the separation roller 20 and the case 26 are sandwichedbetween the pin 40 and the snap ring 45, and thus prevented from beingdetached from the drive shaft 27 or moving in the axis line direction ofthe drive shaft 27. Further, even though a centrifugal force acts on thepin 40 through rotation of the drive shaft 27, the canopy 43 preventsthe pin 40 from being off the drive shaft 27.

When the drive shaft 27 is rotated in a predetermined direction(clockwise in FIG. 12B) by a drive motor (not shown) and the pin 40comes into contact with the engagement projection 44, the separationroller 20 is rotated clockwise in FIG. 12B and a feeding operation isstarted. When a leading end of a document sheet 9 separated is pinchedbetween the feed rollers 15 and a pinch roller (a driven roller) 46 (seeFIG. 13) at a downstream side relative to the separation roller 20 inthe sheet feeding direction, since a circumferential velocity (a feedingspeed) there is slightly higher than that at the separation roller 20,the engagement projection 44 of the separation roller 20 is away in therotating direction from the pin 40. In this situation, no driving forceis transmitted from the drive shaft 27 to the separation roller 20. Whena tail end of the sheet 9 completely passes through the nipping point Nbetween the separation roller 20 and the separation arm 23, theseparation roller 20 stops rotating once. When the pin 40 of the driveshaft 27 being rotating catches up with the engagement projection 44,the separation roller 20 is again rotated by the driving force from thedrive shaft 27. Thus, since the document sheets 9 stacked on thedocument loading table 14 are fed with an appropriate interval between aprecedent sheet and a following sheet, it is possible for the scannerunit 8 of the image scanner 1 to scan the document sheets 9 distinctlyon a sheet-by-sheet basis.

In addition, as illustrated in FIG. 13, the support frame 33 a isprovided integrally with a bank member 47, which is disposed between thenipping point N and a downstream nipping point N1 between the feedrollers 15 and the pinch roller 46 and configured to switch a carryingpath of the fed document sheets 9 from an upward path to a downwardpath. Thereby, it is possible to prevent nipping a sheet 9 between theseparation roller 20 and the separation arm 23 from being improperlyreleased by a downward external force, larger than a pressing force bythe spring plate 24, which might be applied to the separation arm 23when a tensile force acts on the sheet 9 between the nipping point N andthe downstream nipping point N1.

Hereinabove, the embodiments according to aspects of the presentinvention have been described. The present invention can be practiced byemploying conventional materials, methodology and equipment.Accordingly, the details of such materials, equipment and methodologyare not set forth herein in detail. In the previous descriptions,numerous specific details are set forth, such as specific materials,structures, chemicals, processes, etc., in order to provide a thoroughunderstanding of the present invention. However, it should be recognizedthat the present invention can be practiced without reapportioning tothe details specifically set forth. In other instances, well knownprocessing structures have not been described in detail, in order not tounnecessarily obscure the present invention.

Only exemplary embodiments of the present invention and but a fewexamples of its versatility are shown and described in the presentdisclosure. It is to be understood that the present invention is capableof use in various other combinations and environments and is capable ofchanges or modifications within the scope of the inventive concept asexpressed herein. For example, the following modifications are possible.

In some aspects of the present invention, the pickup roller 21 may notnecessarily have to be provided. For example, when the document loadingtable 14 is tilted at a large angle down to the lower circumferentialsurface of the separation roller 20, a stack of document sheets 9 placedon the document loading table 14 slides down along the document loadingtable 14 and automatically establishes contact with the circumferentialsurface of the separation roller 20.

In some aspects of the present invention, various kinds of material suchas metal, other than resin, may be applied to the guide member 25 andthe guide portion 25 c that are configured to apply lower frictionalresistance to a document sheet 9 in contact therewith than theseparation arm 23.

Further, the separation feed mechanism 11 in some aspects of the presentinvention may be applied to a device configured to feed sheets stackedon a feed tray to a printer unit separately on a sheet-by-sheet basis,or to a feeder unit of an automatic counter for banknotes, as well asautomatic sheet feeding to the scanner unit 8.

In the aforementioned embodiments, the document feeder 2 is configuredto feed the document sheets 9 stacked on the document loading table 14sequentially in the order from the top sheet of the document sheets 9.However, aspects of the present invention may be applied to a documentfeeder configured to feed stacked sheets sequentially in the order froma bottom sheet of the stacked sheets.

What is claimed is:
 1. A sheet feeder, comprising: a document holdingtable configured to hold a stack of sheets, such that the stack ofsheets is fed, one by one, from the holding table along a sheet feedingpath, wherein the document holding table is arranged on a first side ofthe sheet feeder; a separation arm comprising a first surface and asecond surface opposite to the first surface, wherein the separation armis arranged on the first side of the sheet feeder; a separation rollerdisposed above the first surface of the separation arm, wherein theseparation roller is arranged on a second side of the sheet feederopposite to the first side of the sheet feeder, and wherein the firstside of the sheet feeder is separated from the second side of the sheetfeeder by the sheet feeding path; an urging member urging the separationarm from the second surface toward the separation roller; and a guidemember arranged on the first side of the sheet feeder, wherein the guidemember comprises an end portion and an intermediate portion, wherein theintermediate portion is provided on the first surface of the separationarm and extends along the first surface of the separation arm, andwherein the end portion is tilted upward from the intermediate portiontoward the separation roller, wherein the separation arm and theseparation roller nip a sheet therebetween at a nipping point, whereinthe end portion of the guide member is disposed at an upstream side ofthe nipping point in a sheet feeding direction, wherein the guide memberextends from underneath the stack of sheets to a downstream side of thestack of sheets in the sheet feeding direction, and wherein a frictionalcoefficient between the guide member and the separation roller is lowerthan a frictional coefficient between the separation arm and theseparation roller.
 2. The sheet feeder according to claim 1, wherein theend portion and the intermediate portion are disposed within a length ofthe separation arm in an axial direction of the separation roller. 3.The sheet feeder according to claim 1, wherein the end portion of theguide member is configured to be elastically bent and form a gap throughwhich a sheet can pass when the sheet fed by the separation roller comesinto contact with the end portion of the guide member.
 4. An imagescanner, comprising: a sheet feeder configured to feed document sheetsin a predetermined direction sequentially on a sheet-by-sheet basis; anda scanner unit configured to scan images on the document sheets fed bythe sheet feeder, wherein the sheet feeder comprises: a document holdingtable configured to hold a stack of sheets, such that the stack ofsheets is fed, one by one, from the holding table along a sheet feedingpath, wherein the document holding table is arranged on a first side ofthe sheet feeder; a separation arm comprising a first surface and asecond surface opposite to the first surface, wherein the separation armis arranged on the first side of the sheet feeder; a separation rollerdisposed above the first surface of the separation arm, wherein theseparation roller is arranged on a second side of the sheet feederopposite to the first side of the sheet feeder, and wherein the firstside of the sheet feeder is separated from the second side of the sheetfeeder by the sheet feeding path; an urging member urging the separationarm from the second surface toward the separation roller; and a guidemember arranged on the first side of the sheet feeder, wherein the guidemember comprises an end portion and an intermediate portion, wherein theintermediate portion is provided on the first surface of the separationarm and extends along the first surface of the separation arm, andwherein the end portion is tilted upward from the intermediate portiontoward the separation roller, wherein the separation arm and theseparation roller nip a sheet therebetween at a nipping point, whereinthe end portion of the guide member is disposed at an upstream side ofthe nipping point in a sheet feeding direction, wherein the guide memberextends from underneath the stack of sheets to a downstream side of thestack of sheets in the sheet feeding direction, and wherein a frictionalcoefficient between the guide member and the separation roller is lowerthan a frictional coefficient between the separation arm and theseparation roller.
 5. The image scanner according to claim 4, whereinthe end portion and the intermediate portion are disposed within alength of the separation arm in an axial direction of the separationroller.
 6. The image scanner according to claim 4, wherein the endportion of the guide member is configured to be elastically bent andform a gap through which a sheet can pass when the sheet fed by theseparation roller comes into contact with the end portion of the guidemember.
 7. An image printing device, comprising: an image scanner thatcomprises: a sheet feeder configured to feed document sheets with imagesthereon in a predetermined direction sequentially on a sheet-by-sheetbasis; and a scanner unit configured to scan the images on the documentsheets fed by the sheet feeder; a feed unit configured to feed printsheets; and a printer unit configured to print the images scanned by thescanner unit onto the print sheets fed by the feed unit, wherein thesheet feeder comprises: a document holding table configured to hold astack of sheets, such that the stack of sheets is fed, one by one, fromthe holding table along a sheet feeding path, wherein the documentholding table is arranged on a first side of the sheet feeder; aseparation arm comprising a first surface and a second surface oppositeto the first surface, wherein the separation arm is arranged on thefirst side of the sheet feeder; a separation roller disposed above thefirst surface of the separation arm, wherein the separation roller isarranged on a second side of the sheet feeder opposite to the first sideof the sheet feeder, and wherein the first side of the sheet feeder isseparated from the second side of the sheet feeder by the sheet feedingpath; an urging member urging the separation arm from the second surfacetoward the separation roller; and a guide member arranged on the firstside of the sheet feeder, wherein the guide member comprises an endportion and an intermediate portion, wherein the intermediate portion isprovided on the first surface of the separation arm and extends alongthe first surface of the separation arm, and wherein the end portion istilted upward from the intermediate portion toward the separationroller, wherein the separation arm and the separation roller nip a sheettherebetween at a nipping point, wherein the end portion of the guidemember is disposed at an upstream side of the nipping point in a sheetfeeding direction, wherein the guide member extends from underneath thestack of sheets to a downstream side of the stack of sheets in the sheetfeeding direction, and wherein a frictional coefficient between theguide member and the separation roller is lower than a frictionalcoefficient between the separation arm and the separation roller.
 8. Theimage printing device according to claim 7, wherein the end portion andthe intermediate portion are disposed within a length of the separationarm in an axial direction of the separation roller.
 9. The imageprinting device according to claim 7, wherein the end portion of theguide member is configured to be elastically bent and form a gap throughwhich a sheet can pass when the sheet fed by the separation roller comesinto contact with the end portion of the guide member.